Open a Mailbox in Outlook
TenantCore can give a licensed Exchange Online user delegated access to TenantCore-created mailboxes. This lets you work with replies in Outlook without assigning a separate Microsoft licence to every sending mailbox.Before you begin
Your BYOT tenant needs an eligible licensed Exchange Online user. That user becomes the Mailbox Access Account.Open the mailbox workflow
- Open Mailboxes.
- Choose Open Mailbox for the mailbox you want to access.
- Select an eligible licensed user.
- TenantCore begins assigning access.
- Full Access
- Send As
Wait for permission verification
The UI can show Assigning access… while Microsoft applies the permissions. Do not assume the permissions are ready just because Microsoft accepted the initial request. TenantCore verifies the delegated state before treating the mailbox as ready.Sign in correctly
When Outlook opens, sign in with the Mailbox Access Account you selected. The Mailbox Access Account is the licensed Microsoft user. The TenantCore-created mailbox remains the mailbox identity you are opening and sending as.If Outlook does not open the mailbox
Microsoft delegation can take time to propagate. If access does not work:- confirm you signed in with the assigned access account
- wait for Microsoft propagation
- return to TenantCore and check delegation status
- use the repair/reapply action if available
- confirm the selected user still has a valid Exchange licence
Changing the access account
For BYOT tenants, TenantCore can change the selected Mailbox Access Account. The safer sequence is:- grant and verify access for the new user
- confirm it is healthy
- remove the old delegation